1. Field of the Invention
The present invention relates to disk drives. More particularly, the present invention relates to disk drives, head stack, gimbal and suspension assemblies that include structures that contribute to reducing disk flutter induced track mis-registration (“TMR”).
2. Description of the Prior Art
A typical hard disk drive includes a head disk assembly (“HDA”) and a printed circuit board assembly (“PCBA”). The HDA includes at least one magnetic disk (“disk”), a spindle motor for rotating the disk, and a head stack assembly (“HSA”) that includes a slider with at least one transducer or read/write element for reading and writing data. The HSA is controllably positioned by a servo system in order to read or write information from or to particular tracks on the disk. The typical HSA has three primary portions: (1) an actuator assembly that moves in response to the servo control system; (2) a head gimbal assembly (“HGA”) that extends from the actuator assembly and biases the slider toward the disk; and (3) a flex cable assembly that provides an electrical interconnect with minimal constraint on movement.
A typical HGA includes a load beam, a gimbal attached to an end of the load beam, and a slider attached to the gimbal. The load beam has a spring function that provides a “gram load” biasing force and a hinge function that permits the slider to follow the surface contour of the spinning disk. The load beam has an actuator end that connects to the actuator arm and a gimbal end that connects to the gimbal that supports the slider and transmits the gram load biasing force to the slider to “load” the slider against the disk. A rapidly spinning disk develops a laminar airflow above its surface that lifts the slider away from the disk in opposition to the gram load biasing force. The slider is said to be “flying” over the disk when in this state.
A challenge faced by hard disk drive designers and manufacturers as they continually increase the capacities of contemporary hard disk drives is the phenomenon known as Non Repeatable Run Out (“NRRO”). NRRO, either written into the data tracks (usually denoted “RRO”) or occurring live during drive operation, manifests itself as radial displacements of the read/write head(s) relative to the data tracks of the disk(s), caused by vibrations of either the HSA or disk pack (inc. spindle motor, disk(s), spacer(s), and clamp). As the storage capacity of magnetic disks increases, the number of data tracks per inch (“TPI”) is increased, or conversely, the track width is decreased, leading to greater data density per unit area on the magnetic media. Since NRRO may degrade the data transfer performance to and from the magnetic media by increasing, for example, the frequency of off track errors, the ratio of RMS NRRO to track width must be maintained at a fairly constant value; thus, designers must ensure that NRRO decreases in proportion to track width. Since disk flutter (or out of plane vibrations of the disk induced by turbulent airflow within the drive) TMR is the dominant contributor to NRRO, reducing disk flutter TMR will correspondingly decrease NRRO. In turn, decreasing NRRO may enable higher TPI to be reliably achieved.
What are needed, therefore, disk drives, head stack and gimbal assemblies, suspensions and load beams configured to reduce disk flutter induced TMR.